How to investigate undefined symbol errors?

[שחר לנגבהיים‎]

Hi,
I'm trying to build Skia, integrate it into my c++ code, and then build it into WASM, but when I call emcc I get several undefined symbol errors, which don't happen with equivalent clang compilation. 

What should I do in order to investigate why these symbols weren't compiled or linked? Is there some verbose output I could go into in order to understand the difference between clang and emcc's behavior?

[Shlomi Fish]

Hi Shachar!

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[Shlomi Fish]

Hi,

CCing the list - see:

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On Wed, 5 Jun 2019 14:25:50 +0300
Shachar Langbeheim <nih...@gmail.com> wrote:

> Hi Shlomi,
> Making an SSCC example will be impossible, since I'm having an issue
> specifically with usage of the Skia library, which is neither small nor
> self contained :). That's why I asked for ways to for me to analyze the
> issue, rather than for you to solve this.
> I'd be happy to write an SSCC example that includes a git submodule of
> Skia, if someone is willing to delve into the issue, but ATM all I'm asking
> for is just an explanation of the modus operandi needed to analyze such
> issues.
>

such a git repo will help a lot, and I can try looking into it.

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[Shachar Langbeheim]

Sorry, and thanks for your corrections.

I uploaded the minimal example to here - https://github.com/Shachlan/skia-wasm-example 

The Readme.md file at the base directory contains the instructions on how to reproduce this. I packed all of the different stages into 3 scripts, in order to ease your process.

Thanks in advance for the help!

[Alon Zakai]

Running with EMCC_DEBUG=1 in the env will print out the linking command etc. Then you can use llvm-nm to look for symbols in those files, which can help debug things like this.

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[Shlomi Fish]

On Wed, 5 Jun 2019 17:45:18 +0300
Shachar Langbeheim <nih...@gmail.com> wrote:

> Sorry, and thanks for your corrections.
>
> I uploaded the minimal example to here -
> https://github.com/Shachlan/skia-wasm-example
> The Readme.md file at the base directory contains the instructions on how
> to reproduce this. I packed all of the different stages into 3 scripts, in
> order to ease your process.
>
> Thanks in advance for the help!
>

Hi,

see https://github.com/Shachlan/skia-wasm-example/issues/1 .

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[Shachar Langbeheim]

Have you pulled the latest commit? It contains the Skia submodule.